This invention relates to an egg containing iron or vitamin D.sub.3 in a high content. Iron is one of the nutrients tending to be deficient, particularly for woman. It was reported that about 50% of adult women and about 70% of senior high school woman students are deficient in iron, containing latent iron deficiencies, and therefore, supplementation of iron is necessary ("Nippon Naika Gakkai Hokoku (Japanese Internal Medicinal Society Report)" 1988) In the case of pregnant women, iron requirement is increased, and it is necessary to take iron about twice as much as an ordinary person. Iron requirement per one day for Japanese people (Ministry of Health and Welfare) is shown in Table 1.
TABLE 1 ______________________________________ Iron Requirement (Ministry of Health and Welfare) Age Iron (mg/l day) (years old) Man Woman ______________________________________ 0 6 6 1 7 .fwdarw. 8 7 .fwdarw. 8 6 9 .fwdarw. 10 9 .fwdarw. 10 11 12 12 20 10 12* 60 10 10 Pregnant Woman -- 15 in the first half period Pregnant Woman -- 20 in the latter half period Lactation Period -- 20 ______________________________________ *After menopause: 10 mg
Incidentally, iron is a mineral resistant to absorb, and only about 10% of intake is absorbed. Particularly, recent foods contain phosphorus additives abundantly, and persons deficient in iron are further increased by the inhibition of the additives from the absorption of iron. Under such conditions, it is necessary to supplement iron in some form for women, particularly pregnant women. Thereupon, various foods for iron supplement have been proposed.
However, the above foods for iron supplement are processed foods wherein inorganic iron agent was added, and therefore, iron absorbability is inferior. Iron agent is also supplied as a medicine to remedy anemia, and in that case, an adverse reaction to reduce gastric functions tends to occur.
The applicants have already developed a feed containing a ferrous salt of organic acid obtained by dissolving an organic acid having reducing action together with a ferrous salt, and the feed was fed to egg-producing chickens (Japanese Patent KOKAI No. 63-148937). By feeding the feed, egg production rate and tail picking trouble were improved, but the improvement in iron content of egg has not been known yet.
On the other hand, it is known that, when vitamin D.sub.3 is deficient, persons fall into rickets because calcification of bones does not proceed normally. That is, vitamin D.sub.3 is necessary for the absorption of calcium (Ca) through intestines. When the vitamin is deficient, Ca absorbability is reduced resulting in the inhibition of bone calcification. When vitamin D is insufficient, however calcium is taken abundantly, most of the calcium taken is excreted without use resulting the occurrence of calcium deficiency.
There are two representative kinds of vitamin D which are D.sub.2 and D.sub.3. Vitamin D.sub.3 has Ca absorption effect on mammals and birds, but vitamin D.sub.2 does not have the effect on birds.
Foods containing vitamin D are unevenly distributed which are fish meats, the yolk of chicken egg, milk and the like among animal foods and shiitake mushroom among vesitable foods. The other foods contain no or only very small amount of vitamin D.
On the other hand, skin contains vitamin D.sub.3 precursor which is converted to vitamin D.sub.3 by ultraviolet irradiation in the sunlight. However, the conversion is not so much in the people whose indoor life is long, such as aged people, and in the people who lives in the district where sunshine time is short. The supplementation of vitamin D is necessary for such a people. Furthermore, bone fracture increases among infants and young people, and the necessity increases for babies and infants to take vitamin D sufficiently who are in the growth stage of bones. Moreover, aged people increases recently. It is said that aged persons, particularly post menopaused women, tend to suffer from osteoporosis wherein bones become fragile and are liable to be fractured, and in 2000 A.D., about 35% of women 60-64 years old, 50% of women not less than 65 years old will suffer from osteoporosis. Thus, the remedy of this disease becomes an important problem as a national disease.
As mentioned above, vitamin D performs a very important role in human body, and now, vitamin D requirement is 400 IU/day for baby, infant (not more than 5 years old), 100 IU/day for young person (not less than 6 years old) adult, and 400 IU/day for pregnant woman, lactating woman.
However, it is difficult for babies, infants, pregnant women and lactating women to take 400 IU vitamin D necessary therefor from foods. In order to take the above amount of vitamin D, 14 eggs or 3 liters of milk must be taken per one day, and such an amount of egg or milk cannot be taken through usual meals. Accordingly, vitamin D must be supplemented by taking a medicine containing various vitamins. In U.S. and Canada, there is a milk fortified by about 400 IU of vitamin D.sub.3 per one pack (1 l) for the purpose of the supplementation of vitamin D.
The applicant have already developed an egg containing vitamin D.sub.3 in a high content by feeding bile acid and not less than 400 IU/day of vitamin D.sub.3 to egg-producing chickens (Japanese Patent KOKAI No. 4-11849).